In order to improve the reliability of data storage in a storage system, data are stored after being multiplexed (duplexed, for example) in a plurality of logical volumes and, in cases where a fault or the like occurs with any logical volume, data restoration is performed by utilizing the data of another logical volume.
As technology that utilizes data duplexing, technology that performs high-speed restoration based on a data update history in cases where a fault occurs in one of the duplexed systems has been disclosed (See Japanese Application Laid Open'No. 2007-86972, for example). Further, a technology that reduces the processing load of a higher level device when data are duplexed is also known (See Japanese Application Laid Open No. 2005-196490, for example). Further, technology that performs a high-speed restore with respect to storage constituting the source from storage which is the target when data duplexing is performed is also known (Japanese Application Laid Open No. 2005-339554, for example).
In addition, a backup server system that improves the reliability of data storage more reliably and at a lower cost by saving duplexed data to a magnetic tape cartridge is known.
FIG. 1 illustrates a backup server system according to a conventional example.
In a backup server system 100, a task server 101 stores data which are used in the task in a P-Vol (Primary Volume) 105 of a disk array device 102 and, in the disk array device 102, data which are written to the P-Vol 105 are duplexed to an S-Vol (Secondary Volume) 106 with predetermined timing. Thereafter, a backup server 103 backs up the data of the S-Vol 106 to tape cartridge 107 of a tape library device 104. Thereafter, when data restoration is performed, the backup server 103 reads data from the tape cartridge 107 by means of a tape library device 104 and stores this data in the S-Vol 106. As a result, the data of the S-Vol 106 can be restored. Subsequently, by starting a reverse copy from the S-Vol 106 to the P-Vol 105, in the case of a low load task, the task server 101 is able to re-start the task utilizing the P-Vol 105. However, in the case of a high load task, when the host access performance drops as a result of the reverse copy from the S-Vol 106 to the P-Vol 105, the task cannot be re-started until the reverse copy is complete.
According to the technology of the above backup server system, the S-Vol 106 that holds the backup is restored, whereupon the task can be re-started by re-starting the reverse copy to the P-Vol 105.
However, in a task restart immediately after restoring the S-Vol 106, the data have not been completely restored to the P-Vol 105. Hence, in cases where read access to an uncopied region of the P-Vol 105 takes place, a response to the host device can only be made after copying from the S-Vol 106. Further, data required for the parity generation of the RAID configuration must be copied from the S-Vol 106 even when the P-Vol 105 is write-accessed. As a result, the host access performance is reduced still further.
In order to prevent a drop in the host access performance of this kind, a direct, restore operation from the tape cartridge to the P-Vol 105 has been considered.
In this case, the user unmounts the P-Vol 105 from the task server 101 and mounts the P-Vol 105 on the backup server 103. The user then'designates the tape cartridge 107 for storing the backup data of the S-Vol 106 corresponding with the P-Vol 105 that the user has mounted on the backup server 103, and instructs the P-Vol constituting the restore destination to execute a restore to the P-Vol 105. Thereafter, the user unmounts the P-Vol 105 from the backup server 103 and mounts the P-Vol 105 on the task server 101. As a result, the task can be restarted if the task is a low load task. In such a case, because there is no need to read-access the S-Vol 106 in the case of read access and write access by the task server 101, there is no drop in the host access performance as a result of accessing the S-Vol 106.
Thereafter, by performing a copy from the P-Vol 105 to the S-Vol 106, a task can be performed without hindrance following copy completion even in the case of a high load task. In addition, following restore completion to the P-Vol 105, the high-load task is started immediately, whereupon an operation in which a copy is made from the P-Vol 105 to the S-Vol 106 in a low load time band such as at night or during a holiday is also possible.
However, in cases where a restore to the P-Vol 105 is performed, the user must perform an operation of the kind described earlier, which is time-consuming. Moreover, it is necessary to designate the P-Vol 105 rather than the S-Vol 106 which is the save source of the data as the restore destination for the data from the tape cartridge, and there is a risk of error in this designation. In addition, whereas the user is normally conscious of the logical volume name of the OS file system, in a basic operation, the user must be conscious of the LU of the disk array device. In addition, in the case of a user with no detailed knowledge of the disk array device 102, there is also the problem that it is difficult to find out the P-Vol 105 which corresponds with the S-Vol.